Illuminating appliance.



L. ILLUMINATIN I IIIIIIII E.

UNITED ST TES OFFICE.

ILLUMINATING APPLIANCE.

To all whom it may concern:

Be it known that I, ALFRED WILLIAM BEU'ITELL, a subject of the King of Great Britain, residing at Streathain, London, England, have invented certain new and useful Improvements in Illuminating Appliances, of which the following is a specification. This invention relates to the construction of reflectors or reflecting surfaces having a uniform cross-section throughout their length, such as, for example, may be used with linear sources of light in such manner that the reflectors being of uniform concave section throughout their length and the linear or straight source of light being located in a suitable position within the concavity of the reflector and parallel thereto, the light flux from the light source is reflected toward one side thereof with any given degree of concentration. Prior to my invention such reflectors have been made either of reflecting metal or material having a plane surface or their surface has been formed with corrugations extending either longitudinally of the reflector and parallel thereto or at right angles thereto. Such reflectors have been open to the objection that being formed according to any given section calculated to produce a given distribution of reflected light flux, irregularities, no matter how small, were necessarily encountered in the actual practice of manufacturing such reflectors, and these irregularities produced striae or streaks of light when the reflector was used, owing to certain portions of the concave surface thereof being of greater or less curvature than that for which they might have been calculated, or inother words, different from the theoretically correct curve.

According to my present invention, slight corrugations are formed continuously in the reflecting surface obliquely to the axis thereof, whereby this streakiness in the reflected light is avoided or largely modified. Before proceeding to describe the action of such corrugations I will first explain the reason of the streaks of light or uneven illumination referred to..- Suppose, for example, a sheet of polished metal having a planesurface to be bent so as to have a uniform crosssection throughout its length, which crosssection is parabolic in form. Theoretically the light flux falling on the reflector would Specification of Letters Patent.

'flector. tions would be displaced laterally with re- Patented Mar. 7, 1916.

Application filed December 21, 1912. Serial No. 737,957.

be reflected in parallel lines and would furbe termed the focal axis of this reflector and considering a very narrow strip taken along any part of the reflector and parallel thereto, such a strip would form what may be called a line-reflection which will be a straight line corresponding to the strip itself. Also the intensity at any point of sucha line reflection would vary gradually along its length according to the distance of such point from the point source of light. Taking a number of such strips next to each other and having regard to the irregularities hereinbefore mentioned, the corresponding line-reflections, instead of being contiguous and forming a gradually varying illumination, such line-reflections or some of them would be, superimposed upon others and the streaks of light mentioned above would result. Such a difliculty is not overcome by forming corrugations in the reflector either longitudinally or at right angles to the re- In the former case the line-reflecspect to the position they would otherwise occupy in .the theoretically accurate plane reflector. The straight line-reflections would be superimposed irregularly with resultant streaks of light. In the latter case, considering the line-reflections from asingle strip, portions of the line-reflection proceeding from alternate corrugations would be displaced longitudinally along the line right and left as itwere, but always occupying their positions on the same straight line-reflection. Considering therefore a number of suchcontiguous strips and: the supposed irregularities in the reflector, the result would be as in the case of the plane reflector, the irregular superimposition of a number of straight line-reflections.

Regarding the continuous or linear light source placed along or in the reflector, such a light source would represent merely a number of such point light sources arranged in line and the effect described above would be similar or intensified. Now according to my invention, the corrugations are'formed in the reflecting surface obliquely. A strip a number of straight line-reflections.

taken along the reflector is therefore composed of portions which are obliquely displaced in two differentv planes alternately with the result that the line-reflection therefrom takes the form of a sinuous wave or has alternate parts thereof displaced on 0 posite sides of its center line. It will e seen that the superimposition of a number of such contiguous sinuous line-reflections will result in increased uniformity of illumiration, as compared, with the streaky illumination resulting from superimposli rlilg e corrugations may be formed in the reflecting surface at any desired angle of obliquity; and furthermore, such oblique corrugations may be crossed or arranged crosswise in any.

desired manner.

The operation of reflectors constructed according to the present invention will evidently hold good for circular,'parabolic, hy-

perbolic, elliptical or an other form of reflector, any of which re ectors I may make according to the present invention. Also the reflectingsurface may be made of metal,

sheet metal, silvered glass or any other suitpractice the depth of thedepressions are of the order of the thickness of the metal). The corrugations preferably extend the full width of the reflector, in other words, from one side edge of the reflecting surface to the other side, edge of the same.

pressed or otherwise formed into any desired shapel According to another method I form the corrugations in the metal sheets by pressing or stamping them between suitable dies, the dies being shaped or molded with corrugated surfaces conforming to the required corrugations in the finished reflectors. According to another method I employ sheets of glass fluted or corrugated on the side farthest from the source of light in the same or opposite directions which are coated on the said side farthest removed from the source of light with any suitable reflecting material in the usual well known manner.

Referring now to the accompanying drawings: Figure 1 is a plan view showing a flat re ector, according to the present invention, before the same is bent, rolled or pressed into shape. Fig. 2 is an elevational view of the same where the reflector is made of sheet After being corrugated the sheet is then bent, rolled or arrears.

metal showing the edge thereof. as a single wavy line representing thethickness of the sheet. Fig. 3 is a sectional view (on line 33 Fig. l) where the reflector is made by providing the under surface of a sheet of glass or other transparent material with flutings or corrugations in the manner pre viously described and by coating said under side with a suitable reflectin material as shown in the thick line A. Fig. 4 is a cross sectional view of an illuminating appliance similar to that shown in Fig. 8 of my British Patent No. 24,950 of 1909. This F ig. 4 illustrates the employment of a concave metal reflector in the illuminatin appliance shown in said patent, but-said Fig. 4 is a cross sectional view of the construction shown in Fig. 5. Fig. 5 is a plan view of a lamp and holding means, the latter of which isprovided with one of my new reflectors. This lamp and holding means are similar to the lamp and holding means shown in Fig. 7 of the British patent previously referred to.

In all of the figures I have represented reflectors corrugated only in one direction, as I have found this to be a very practical form of reflector.

Referring again to Fig. 3, while this view is made to show for the sake of simplicity a flat glass sheet provided on one side thereofwith corrugations and a reflecting surface, it is understood that if such sheet were made for a reflector having a concave cross section, as shown in Fig. 4, the glass sheet would be bent or molded first and provided with its reflecting surface afterward.

It is understood that my improved reflectors may be bent or formed in any shape other than that shown in Fig. 4. Also it is understood that I do not confine myself to any of the hereinbefore described methods or to any particular method of manufacturing reflectors according to the present invention.

The improvements herein set forth are not limited to the precise construction and arrangement shown and described as they may be embodied in various forms and moda concave reflecting surface provided with parallel corrugations disposed continuously and obliquely to the longitudinal direction or axis thereof.

4. The combination of an electric lamp having a longitudinally extending linear source of light and a longitudinally extending reflector or reflecting surface which is provided with parallel corrugations that extend continuously and obliquely to the source of light. V

5. The combination of a reflector of substantially uniform cross section throughout its length and provided on its reflecting surface with corrugations extending continuously and obliquely to the longitudinal direction or axis thereof, an incandescent electric lamp having a straight source of light extending in a direction parallel to said axis and means for holding said source of light in position with respect to the reflector.

6. An illuminating appliance comprising an incandescent lamp having a straight incandescent filament section therein, means for supporting the lamp, and a member having a reflecting surface provided with corrugations that extend continuously and obliquely to said filament section.

7. A lighting appliance having in combination therein a longitudinally extending reflecting surface concave in cross section and a' longitudinally extending source of light located within the concavity of said reflecting surface, said reflecting surface being provided with corrugations that extend continuously and obliquely to its longitudinalaxis.

8. An illuminating appliance having a reflecting surface of a substantially uniform concave cross section throughout its length and an incandescent lamp located in front of the concave reflecting surface, said reflecting surface being provided with parallel corrugations which extend obliquely to its longitudinal axis.

9. The combination of an incandescent lamp having straight longitudinally extending filament sections, a concave reflector comprising a glass or other transparent medium having on the side farthest removed from the lamp a corrugated surface which is formed as a reflector, the corrugations therein extending m a direction obliquely to the longitudinal extending axis of said reflector, and means for holding said lamp in position.

This specification signed and witnessed this 3d day of December, A. D. 1912.

Y ALFRED W. BEUTTELL. Signed in'the presence of AUsTIN B. BoLEMAN, EDWIN A. PACKARD. 

